The invention is directed to a circular knitting machine for the production of knitwear having combed-in fibers, also called circular sliver knitting machine.
Knitting machines of this type normally comprise a needle cylinder with knitting needles, a sinker ring with sinkers having upper edges and being mounted so as to be rotatable about an axis of rotation jointly with the needle cylinder, and a stationary cylinder cam and sinker cam means associated with the knitting needles and sinkers, respectively. The cam means form at least one knitting system extending in the rotating direction of the needle cylinder, which knitting system has at least one cylinder cam part for raising and drawing off the knitting needles, yarn and fiber feed means for feeding and inserting the yarn and fiber tufts in raised knitting needles, at least one sinker cam part for advancing and retracting the sinkers and an air guiding unit provided with at least one suction nozzle and/or blowing nozzle. The cylinder cam part and sinker cam part means, the yarn and fiber feed means and the air guiding unit are so constructed and arranged relative to one another that initially loops are formed from the yarn and the fiber tufts with the fiber tufts being directed essentially toward the axis of rotation, and that the direction of the fiber tufts is then substantially reversed by the air guiding unit. The reversed fiber tufts are laid over adjacent sinkers so that they can take part at least once in a loop forming process when passing through the same knitting system or another knitting system.
In circular knitting machines for producing knitwear containing combed-in fibers, also known as high-pile goods, the fibers are normally inserted into the hooks of the knitting needles by means of combing-in cylinders (doffer rolls) in such a way that the free ends of the fibers lie on the back of the needles and on the inner side of the knitwear, i.e., they are directed toward the axis of rotation of the needle cylinder. In order to facilitate the tying in of the fibers and to enable short pile lengths (short-pile goods) without suffering large combing-in losses and shearing losses, circular knitting machines for producing knitwear with combed-in fibers are already known, wherein the position of the fiber tufts inserted in the knitting needles is reversed after loop formation in such a way that their free ends are directed away from the axis of rotation of the needle cylinder, are arranged on the front sides of the knitting needles, lie diagonally over the upper edges of the sinkers and are therefore once again grasped by the knitting needles during the next loop forming process and are tied into the knitwear. Depending on the length of the fibers, these processes can also be repeated a number of times in succession, in which case the fibers which are worked to form a first loop are subsequently tied into the knitwear over several adjacent needle wales at least in the form of loops or tuck loops at a number of locations.
In order to produce short-pile knitwear of this type, which is occasionally also referred to as reverse loop sliver knit fabrics, there are known circular knitting machines (U.S. Pat. No. 4,245,487) having blowing nozzles serving to reverse the ends of the fibers. These blowing nozzles are arranged on the inner side of the needle cylinder, approximately at the location where the knitting needles are gradually raised again after a loop formation in order once again to receive yarns and fibers, and extend substantially radial to the knitting needles. However, apart from the blowing nozzles, these circular knitting machines do not possess means by which it would be possible to reverse the ends of the fibers in a controlled and uniform manner such as would be required for producing saleable knitwear.
In a known circular knitting machine of the generic type mentioned above (U.S. Pat. No. 5,431,029), the reversal of the fibers is likewise carried out by means of blowing nozzles facing radially outward. The chief problem in this respect consists in that a carrier for the cam controlling the sinkers is arranged, considered in the direction of flow, behind the outlet opening of the blowing nozzles, wherein the air jets coming from the blowing nozzles are reflected at the carrier and are deflected upward, so that the reversed fibers are directed away from the knitwear rather than toward the knitwear. In addition, the knitting needles are subjected not only to the air jets of the blowing nozzles, but also to the suction effect of an exhaust hood arranged above the circular knitting machine and that of additional suction nozzles which are arranged on the front sides of the knitting needles and serve to suck out excess and free-floating fibers. Accordingly, not only are there obstructions in the flow paths of the blown air coming from the blowing nozzles which impede the formation of uniform air flows which reliably bring about the reversal of fibers, but there also occurs in the area of the knitting needles compulsorily uncontrollable whirling air which likewise impedes a uniform reversal of fibers. For this reason, the blowing nozzles are accompanied by complicated and technically elaborate adjustment and alignment devices to enable precise adjustment of the blowing nozzles, also depending on the fiber length used in individual cases, and so that the blowing nozzles can be oriented in such a way that a favorable reversal of fibers is achieved. This requires laborious adjustment and alignment work which relies to a great extent on trial and error and should therefore be avoided.